A new road detection unit detects a new road according to a travel locus of a vehicle and road map data of a road map data learning device. The new road is not included in the road map data. A road learning unit learns the new road, which is detected by the new road detection unit, as a learned road being functional additionally to the road map data. A storage device stores a feature of an erroneous new road, which is erroneously detected by the new road detection unit, as learning-prohibited pattern information. The road learning unit restricts learning of a new road detected by the new road detection unit when the feature of the new road detected by the new road detection unit coincides with the learning-prohibited pattern information stored in the storage device.